An ink jet method has been used to fill material, such as color resin, to organic semiconductor film of a display or to a color filter to manufacture liquid crystal panels for color display.
When material is filled by an ink jet method, it is necessary to form partition elements to partition pixel areas (hereafter also called “banks”, a layer to form partition elements is called a “bank layer”), and to fill a thin film material solution to the area enclosed with the partition elements. A thin film material solution, which volume is much larger than the volume after film formation, is filled in the pixel area enclosed with the partition elements. Since a display is generally demanded to be slim, the height of the partition elements is limited. Therefore the behavior of the thin film material solution filled there differs depending on the wettability (affinity) which the partition elements and the area enclosed with the partition elements have for the thin film material solution.
If the partition elements have affinity for the material, the material easily flows over to the adjacent pixel areas, even if the partition elements exist, when an amount of material exceeding the height of the partition elements is filled, as shown in FIG. 9A. If the partition elements have no affinity for the material, the material does not flow over to the adjacent pixel areas due to the surface tension of the material, even if the amount of material exceeding the height of the partition materials is filled, as shown in FIG. 9B. If this material is heated to evaporate the solvent, thickness after film formation becomes thick at the center of the pixel area and thin at the edges, since the material is repelled by the side walls of the partition elements, as shown in FIG. 9C. This causes color unevenness and reduces reliability. Also if the partition elements are comprised of non-affinity elements, adhesion of the partition elements and ground plane of the partition elements is weak, which makes partition elements easily separate.
A prior art to solve such problems is a surface treatment technology to make the top of the partition elements have no affinity and to make the other portions have affinity. Japanese Patent Laid-open No. 9-203803 and Japanese. Patent Laid-open No. 9-230129, for example, disclose a technology to process the top portion of the partition elements to be ink repellent by irradiating ultraviolet rays, and the area enclosed with the partition elements to have affinity for ink. For the former, an ink repellent (non-affinity) layer is coated at the top portion of the partition elements, and for the latter, the concave portion enclosed with the partition elements is made to have affinity for ink (affinity) by ultraviolet irradiation. Logical considerations of this technology are written in International Display Research Conference 1997, pp. 238-241. According to this technology, even if material is filled to the height exceeding the height of the partition elements, the material is repelled by the non-affinity film, and does not overflow to the adjacent pixel areas, as shown in FIG. 10A, since the side walls of the partition elements have affinity, and the thickness of formed film does not become thin at the edges of the pixel areas.
However, even in the above known technology, it is not clear how to set affinity of the side walls of the partition elements, therefore it is difficult to obtain a flat thin film layer. Japanese Patent Laid-open No. 9-230129 states that the degree of affinity is controlled by irradiating ultraviolet rays from both the front and back sides, but the degree of affinity and non-affinity, that is, how to set the respective contact angle to the thin film material solution, is not known.
If the non-affinity is too high, for example, the thin film layer becomes thin at the edges near the partition elements and thick at the center as shown in FIG. 9C. If affinity is too high, on the other hand, the thin film layer becomes thick at the edges near the partition elements and thin at the center as shown in FIG. 10B.
Also the above known technology assumes that there is only one thin film layer, therefore it is totally unknown how to treat the surface for forming a flat thin film layer for each layer when multi-layered thin film layers are formed. If the above known technology is applied for each layer, surface treatment is required each time a layer is formed, which requires numerous processing steps.